Technical Field
Disclosure of the present application relates generally to a field device and a detector wherein a detector includes a sensor converts a measurement signal into a physical quantity and transmits the physical quantity as digital data to a converter. Disclosure of the present application also relates to a detector in which a detector includes a sensor converts a measurement signal into a physical quantity and outputs the physical quantity as digital data.
Related Art
Conventionally, in a field device in which a detector includes a sensor and a converter for converting a measurement value into a unified instrumentation signal and outputting the unified instrumentation signal are separate, all electric circuits required for calculation are mounted on the converter side, and the converter performs a process of converting a measurement signal which is analog-transmitted from the detector into a physical quantity, converting the physical quantity into a unified instrumentation signal, and outputting the unified instrumentation signal to the outside.
In recent years, intelligentization of field devices has been in progress, and a field device referred to as a smart sensor that converts a measurement signal into a measurement value which is a physical quantity on the detector side and transmits the obtained measurement value as digital data to the converter is being put to practical use.
FIG. 4 is a block diagram illustrating a configuration example of a conventional smart sensor 500. The smart sensor 500 includes a detector 510 and a converter 520, which are connected by a cable 530.
The detector 510 includes a first microprocessor 511, a random access memory (RAM) 512, a read-only memory (ROM) 513, a sensor 514, an amplifier 515, a filter 516, an analog-to-digital (A/D) converter 517, and an internal power source 518. In the example of FIG. 4, measurement systems including a system A and a system B are assumed to be provided, and the sensor 514, the amplifier 515, the filter 516, and the A/D converter 517 are provided in two systems corresponding to the system A and the system B.
In each of the systems, an analog measurement signal acquired by the sensor 514 is amplified by the amplifier 515, a required band is extracted by the filter 516, and then the analog measurement signal is converted into a digital form by the A/D converter 517.
Then, the first microprocessor 511 performs calculation using the RAM 512 and the ROM 513, thereby converting the digital signal into a measurement value which is a physical quantity and outputting the obtained measurement value as digital data to the converter 520 via the cable 530.
The converter 520 includes a second microprocessor 521, a RAM 522, a ROM 523, a 4-20 mA current output circuit 524, and an internal power source 525. The second microprocessor 521 receives the digital data transmitted from the detector 510 and performs predetermined processing on the digital data by using the RAM 522 and the ROM 523. The 4-20 mA current output circuit 524 converts the measurement value into a 4-20 mA direct current which is a unified instrumentation signal and outputs the 4-20 mA direct current to an external device 540.
Power is supplied to the smart sensor 500 from the external device 540 via a signal line that outputs the 4-20 mA direct current. The smart sensor 500 uses the supplied power as the internal power source 525 of the converter 120 and also supplies the power to the internal power source 518 of the detector 510 via the cable 530.
Japanese Unexamined Patent Application, First Publication No. H10-221132 is an example of the above-described related art.
When trouble occurs in the detector 510, there is a need to analyze a measurement signal output from the sensor 514 to find the cause, or the like. Generally, the detector 510 installed on site is often installed in a place that is difficult for an operator to enter or work. Consequently, in such a case, the analysis is performed using the digital data output by the first microprocessor 511.
However, because the digital data output by the first microprocessor 511 is a result of the A/D converter 517 discretizing (digitizing) the measurement signal output from the sensor 514 and the first microprocessor 511 converting the discretized measurement signal into a measurement value which is a physical quantity, the digital data is not necessarily suitable for the analysis of the measurement signal.
Thus, an objective of the present invention is to facilitate analysis of a measurement signal of a sensor in a field device in which a detector includes a sensor converts a measurement signal into a physical quantity and transmits the physical quantity as digital data to a converter. Another objective of the present invention is to facilitate analysis of a measurement signal of a sensor also in a converter in which a detector includes a sensor converts a measurement signal into a physical quantity and outputs the physical quantity as digital data to the outside.